1. Construction speed
1. High excavation efficiency
- TBM uses mechanical cutting to excavate continuously. Under suitable geological conditions, its excavation speed is relatively stable and fast. For example, in some soft rock or soil tunnels, the daily excavation distance of TBM can reach several meters or even tens of meters.
- The traditional drilling and blasting method requires a series of processes such as drilling, charging, blasting, ventilation and exhaust, and slag removal. Each cycle takes a long time, and after blasting, the face needs to be inspected and cleaned for safety, resulting in a relatively slow overall excavation speed.
2. Strong construction continuity
- TBM can carry out excavation operations uninterruptedly. Except for regular maintenance and sudden failures of equipment, long-term shutdowns rarely occur.
- Due to the danger of blasting operations and the impact on the surrounding environment, the traditional drilling and blasting method has a limited number of blastings per day, and a lot of preparation and finishing work is required before and after blasting, and the construction continuity is poor.
2. Construction safety
1. Higher safety
- During TBM construction, operators work under the protection of the shield, which can effectively avoid dangers such as tunnel collapse and rockfall. The shield can withstand the pressure of the surrounding rock and soil, providing a relatively safe working space for construction personnel and equipment.
- Traditional drilling and blasting methods have greater safety risks during the blasting process, such as accidental explosions, flying rocks and toxic gas leaks caused by explosives. In addition, the stability of the tunnel surrounding rock after blasting is poor, and collapse accidents are prone to occur.
2. Reduced difficulty in safety management
- TBM has a high degree of automation, which reduces a large number of manual operations directly involved in dangerous operations, so that the focus of safety management is mainly on the normal operation and maintenance of equipment, which is relatively easy to control.
- Traditional drilling and blasting methods involve more manual operation links, such as drilling, charging, blasting, etc., each link requires strict safety management measures, and management is difficult.
3. Construction quality
1. High excavation accuracy
- TBM can accurately excavate according to the preset trajectory, and its deviation control ability is strong. Generally speaking, the linear accuracy of tunnels excavated by TBM is relatively high, which is very beneficial for projects with strict linear requirements such as high-speed railway tunnels and subway tunnels.
- Due to the impact force and uncontrollability of blasting, it is difficult to accurately control the excavation profile of the tunnel with the traditional drilling and blasting method, and it is easy to over-excavate or under-excavate. Over-excavation will increase the amount of concrete lining, and under-excavation requires secondary blasting or manual finishing, which affects the construction quality and progress.
2. Small disturbance to the surrounding rock
- TBM uses mechanical cutting, which has relatively small disturbance to the surrounding rock. During the excavation process, the shield plays a certain supporting role on the surrounding rock, which is conducive to maintaining the stability of the surrounding rock and reducing the possibility of deformation and collapse of the surrounding rock.
- The impact force generated by the blasting of the traditional drilling and blasting method will cause greater vibration and damage to the surrounding rock, causing a significant change in the original stress state of the surrounding rock, and more support measures need to be taken to ensure the stability of the tunnel.
IV. Environmental protection
1. Low vibration and noise
- TBM construction mainly relies on mechanical cutting, which generates relatively small vibration and noise, and has little impact on the surrounding environment and nearby residents.
- Traditional drilling and blasting operations will produce strong vibration and huge noise, which may cause great interference to surrounding buildings, underground pipelines and residents' lives.
2. Low dust and exhaust gas emissions
- The amount of dust generated during TBM construction is relatively small, and the diffusion of dust can be effectively controlled through the supporting ventilation and dust removal system. For TBMs driven by electricity, no fuel exhaust gas emissions will be generated, which is conducive to improving the construction environment in the tunnel.
